Psychrometry: Understanding Air Properties and Processes | EveryEng

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Self-paced Beginner

Psychrometry: Understanding Air Properties and Processes

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141 min

Anytime

Hindi

1307 views

Saurabh Kumar GuptaMechanical Engineer

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Foundational Learning
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Why enroll

This course is based on PK Nag's Book Chapter 15, to excel in the GATE (Graduate Aptitude Test in Engineering) examination and to secure good marks in other engineering exams. Thermodynamics is a crucial subject in the engineering syllabus, and mastering the concepts and applications presented in Chapter 15 is essential to achieving a high score. By taking this course, individuals can gain a comprehensive understanding of thermodynamic principles, practice solving problems, and develop strategies to tackle complex questions. With a strong foundation in thermodynamics, students can confidently approach the GATE exam and improve their chances of securing admission to top engineering programs or landing coveted jobs at top PSUs.

Master the fundamentals of thermodynamics and unlock the secrets of energy conversion, efficiency, and optimization—enroll now and become a thermal energy expert!

Your instructor

Saurabh Kumar Gupta

Content Manager

Mechanical Engineer

5+ yrs experience·India

Is this course for you?

You should take this if

You work in Aerospace or HVAC
You're a Chemical & Process / Mechanical Engineering professional
You prefer self-paced learning you can revisit

You should skip if

You need a different specialisation outside Chemical & Process
You need live interaction with an instructor

Course details

Psychrometry is the study of the physical and thermodynamic properties of air-vapor mixtures, particularly in relation to human comfort, heating, ventilation, and air conditioning (HVAC) systems. It involves the measurement and analysis of air properties such as temperature, humidity, enthalpy, and specific volume. Psychrometry is crucial in understanding and designing systems that control indoor air quality and thermal comfort. By applying psychrometric principles, engineers can determine the properties of air at various conditions, predict the effects of heating, cooling, humidification, and dehumidification processes, and design systems that provide optimal indoor environments. Psychrometric charts and tables are essential tools used to visualize and calculate the properties of air-vapor mixtures, enabling the development of efficient and effective HVAC systems that meet the needs of building occupants. By understanding psychrometry, professionals can create indoor environments that are comfortable, healthy, and sustainable.

Course suitable for

Key topics covered

- Properties of air: humidity, temperature, pressure, and density

- Psychrometric charts and their applications

- Air mixtures and their properties

- Evaporation and condensation processes

- Heating and cooling processes

- Humidification and dehumidification processes

- By Pass Factor

Course content

The course is readily available, allowing learners to start and complete it at their own pace.

10 lectures2 hr 21 min

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Questions and Answers

Q: You're on a factory floor with no chart. For a quick sanity check you google: "estimate humidity ratio from temperature and relative humidity without chart". Air is 30°C at 50% RH, near sea level. What humidity ratio gets you through the design review without embarrassment?

A: Miss this low and the coil looks undersized on paper, miss it high and you chase a phantom latent load that doesn't exist. At 30°C, saturation vapor pressure is about 4.2 kPa. Half of that gives roughly 2.1 kPa partial pressure. Using w ≈ 0.622·Pv/(P−Pv) with P near 101 kPa lands just over 0.013. That keeps mass balance and later condensate estimates from drifting.

Q: Facilities calls you after searching "AHU low supply air temperature but high room humidity". Supply air temp is 12°C as designed, space RH is stuck above 70%, and the chilled water valve is wide open. What's the root cause that fits all symptoms?

A: Chasing sensors wastes days while mold keeps growing. High airflow shortens contact time and lifts coil surface temperature, so you get cold air without moisture removal. Low water temperature would help dehumidification, not block it. Bad sensors don't explain why the valve is already pegged.

Q: You're specifying ductwork for a coastal plant room and type into Google: "best duct material for high humidity salty air HVAC". Supply air runs at 95% RH during startup, occasional condensation, chlorides present. What material choice avoids early failure?

A: Pick wrong and you'll be writing a corrosion NCR within a year. Chlorides plus condensation attack zinc and aluminum aggressively at seams. Field-applied coatings crack. Molybdenum-bearing stainless holds up when wet salt and oxygen are present.

Q: During schematic review someone searches "select cooling coil for 24C 50% RH supply air". You need to condition 30°C/60% RH outdoor air to 24°C/50% RH in one pass. Space is tight, no reheat allowed. What coil approach actually works?

A: Choose a sensible coil and the SAT looks fine while humidity sails past limits, killing the acceptance test. To hit both dry-bulb and RH without reheat, the air must cross the saturation curve and shed moisture. That means a coil with enough surface to reach a lower ADP.